baylibre-acme: Use timerfd instead of a fake pipe.

Currently baylibre-acme uses a fake pipe as the input channel required by
libsigrok API and calls sleep() in the data acquisition callback to create
intervals between measurements.

Switch to a more elegant approach: use Linux' timerfd and set a periodic
timer equal to the sampling rate. Then read the data every time the timer
expires.

Signed-off-by: Daniel Lezcano <redacted>
Signed-off-by: Bartosz Golaszewski <redacted>

diff --git a/src/hardware/baylibre-acme/api.c b/src/hardware/baylibre-acme/api.c
index 75f2c0446e4f76a94d95e5abe4809b93c7997214..6ec4d7492ddb7d5d5be7e8c41111dc172ae1c825 100644 (file)
--- a/src/hardware/baylibre-acme/api.c
+++ b/src/hardware/baylibre-acme/api.c
@@ -18,6 +18,8 @@
  */
 
 #include "protocol.h"
+#include <time.h>
+#include <sys/timerfd.h>
 
 SR_PRIV struct sr_dev_driver baylibre_acme_driver_info;
 
@@ -349,6 +351,10 @@ static int dev_acquisition_open(const struct sr_dev_inst *sdi)
 static int dev_acquisition_start(const struct sr_dev_inst *sdi, void *cb_data)
 {
        struct dev_context *devc;
+       struct itimerspec tspec = {
+               .it_interval = { 0, 0 },
+               .it_value = { 0, 0 }
+       };
 
        (void)cb_data;
 
@@ -360,19 +366,30 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi, void *cb_data)
 
        devc = sdi->priv;
        devc->samples_read = 0;
+       devc->samples_missed = 0;
+       devc->timer_fd = timerfd_create(CLOCK_MONOTONIC, 0);
+       if (devc->timer_fd < 0) {
+               sr_err("Error creating timer fd");
+               return SR_ERR;
+       }
 
-       if (pipe(devc->pipe_fds)) {
-               sr_err("Error setting up pipe");
+       tspec.it_interval.tv_sec = 0;
+       tspec.it_interval.tv_nsec = (1000000000L / devc->samplerate);
+       tspec.it_value = tspec.it_interval;
+
+       if (timerfd_settime(devc->timer_fd, 0, &tspec, NULL)) {
+               sr_err("Failed to set timer");
+               close(devc->timer_fd);
                return SR_ERR;
        }
 
-       devc->channel = g_io_channel_unix_new(devc->pipe_fds[0]);
+       devc->channel = g_io_channel_unix_new(devc->timer_fd);
        g_io_channel_set_flags(devc->channel, G_IO_FLAG_NONBLOCK, NULL);
        g_io_channel_set_encoding(devc->channel, NULL, NULL);
        g_io_channel_set_buffered(devc->channel, FALSE);
 
        sr_session_source_add_channel(sdi->session, devc->channel,
-               G_IO_IN | G_IO_ERR, 1, bl_acme_receive_data, (void *)sdi);
+               G_IO_IN | G_IO_ERR, 1000, bl_acme_receive_data, (void *)sdi);
 
        /* Send header packet to the session bus. */
        std_session_send_df_header(sdi, LOG_PREFIX);
@@ -398,11 +415,15 @@ static int dev_acquisition_stop(struct sr_dev_inst *sdi, void *cb_data)
        g_io_channel_shutdown(devc->channel, FALSE, NULL);
        g_io_channel_unref(devc->channel);
        devc->channel = NULL;
+       close(devc->timer_fd);
 
        /* Send last packet. */
        packet.type = SR_DF_END;
        sr_session_send(sdi, &packet);
 
+       if (devc->samples_missed > 0)
+               sr_warn("%d samples missed", devc->samples_missed);
+
        return SR_OK;
 }
 

diff --git a/src/hardware/baylibre-acme/protocol.c b/src/hardware/baylibre-acme/protocol.c
index dfd634bb380ee60a121b9b6f5205a5068b7f1fb4..5552ff565bbbad12a2feee85f56e5d42c096e516 100644 (file)
--- a/src/hardware/baylibre-acme/protocol.c
+++ b/src/hardware/baylibre-acme/protocol.c
@@ -560,8 +560,8 @@ SR_PRIV void bl_acme_close_channel(struct sr_channel *ch)
 
 SR_PRIV int bl_acme_receive_data(int fd, int revents, void *cb_data)
 {
-       uint32_t cur_time, elapsed_time, diff_time;
-       int64_t time_to_sleep;
+       uint32_t cur_time, elapsed_time;
+       uint64_t nrexpiration;
        struct sr_datafeed_packet packet, framep;
        struct sr_datafeed_analog analog;
        struct sr_dev_inst *sdi;
@@ -586,16 +586,17 @@ SR_PRIV int bl_acme_receive_data(int fd, int revents, void *cb_data)
        memset(&analog, 0, sizeof(struct sr_datafeed_analog));
        analog.data = &valf;
 
+       if (read(devc->timer_fd, &nrexpiration, sizeof(nrexpiration)) < 0) {
+               sr_warn("Failed to read timer information");
+               return TRUE;
+       }
+
        /*
-        * Reading from sysfs takes some time - try to keep up with samplerate.
+        * We were not able to process the previous timer expiration, we are
+        * overloaded.
         */
-       if (devc->samples_read) {
-               cur_time = g_get_monotonic_time();
-               diff_time = cur_time - devc->last_sample_fin;
-               time_to_sleep = G_USEC_PER_SEC / devc->samplerate - diff_time;
-               if (time_to_sleep > 0)
-                       g_usleep(time_to_sleep);
-       }
+       if (nrexpiration > 1)
+               devc->samples_missed += nrexpiration - 1;
 
        framep.type = SR_DF_FRAME_BEGIN;
        sr_session_send(cb_data, &framep);

diff --git a/src/hardware/baylibre-acme/protocol.h b/src/hardware/baylibre-acme/protocol.h
index 4600211b29b2fe79f16aec44c3ab2b5fe0f3c6d7..a3f4452c12e1d67ae2ce07fdd55e904c133d1985 100644 (file)
--- a/src/hardware/baylibre-acme/protocol.h
+++ b/src/hardware/baylibre-acme/protocol.h
@@ -65,9 +65,10 @@ struct dev_context {
 
        uint32_t num_channels;
        uint64_t samples_read;
+       uint64_t samples_missed;
        int64_t start_time;
        int64_t last_sample_fin;
-       int pipe_fds[2];
+       int timer_fd;
        GIOChannel *channel;
 };